Poly(sodium acrylamidomethyl propane sulfonate), polyacrylamide and partially hydrolyzed polyacrylamide, and copolymers thereof are water soluble polymers that have been previously disclosed in the literature and have found application in the viscosification of aqueous solutions. These polymers viscosify through a combination of high molecular weight and chain expansion due to repulsion of pendant ionic groups along the polymer chain or H-bonding. These polymers are salt-sensitive, thereby limiting their application in highly saline systems.
The betaines are a special class of zwitterions. These materials are self neutralized and contain no counterions. Moreover, the positive and negative charges are separated by alkyl groups.
Carboxymethacrylate betaine monomers (I) and polymers (II) are well-known and disclosed in U.S. Pat. No. 2,777,872 (Jan. 15, 1957), U.S. Pat. No. 2,834,758 (May 13, 1958) and U.S. Pat. No. 2,846,417 (Aug. 5, 1958). ##STR3##
Carboxyvinylpyridine betaine monomers and homopolymers (III) have also been reported [H. Ladenheim and H. Morawetz, J. Poly. Sci. 26, 251 (1957)]. ##STR4##
Sulfovinylpyridine betaine monomers and homopolymers (IV) are known [R. Hart and D. Timmerman, J. Poly. Sci. 28, 118 (1958)] and Ger. Auslegeschrift No. 1,207,630 and Galin, et al., Polymer, 25, 121,254 (1984). ##STR5##
The butylsulfobetaine of poly(2-vinylpyridine) (IVB) is soluble in water, but the butylsulfobetaine of poly(4-vinylpyridine) (IVA) is not. Both betaines are soluble in salt solution.
Methacrylate based sulfobetaine monomers and homopolymers (V) are described by Galin Polymer, 25, 121,254 (1984) and Ger. Auslegeshrift No. 1,207,630, U.S. Pat. No. 3,549,605 and U.S. Pat. No. 3,493,547. ##STR6##
Copolymers of acrylamide and methacrylate and vinyl pyridine betaine monomers, like IV and V, are described in Ger. Auslegeschrift No. 1,207,630.
In turn, copolymers of long chain alkyl acrylamide and acrylamide have been described by Bock, et al. (U.S. Pat. No. 4,520,182). Enhanced viscosification is claimed for the latter materials. Such materials are prepared by special micellar (U.S. Pat. No. 4,528,348) or microemulsion (U.S. Pat. No. 4,521,580) polymerization methods using surfactants like sodium lauryl sulfate (SDS) to incorporate the long chain alkylacrylamide